Because of their excellent mechanical, thermal, and dielectric properties, ceramic materials are widely used as substrates for the production of integrated circuits. A pattern of conductive paste material, corresponding to the desired pattern of conductive pathways, is placed on the surface of a ceramic substrate or module in its green, or unfired, state. The resulting composite is fired to produce conductive pathways on the surface of a sintered ceramic substrate, known as a ceramic module, having high hardness and high mechanical strength. Various electronic devices are added to the module to form an integrated circuit on the surface of the ceramic substrate.
For tracking and quality control reasons, it is necessary to be able to identify and follow an individual ceramic module as it moves through the production process. This requires that each part be "serialized," that is, each ceramic module must be marked with an identifying characteristic, such as a unique sequence of alphanumeric characters.
The current method of part identification is difficult to use and produces characters that vary in size and shape. A sheet of unfired ceramic, known as a green sheet, is moved on a programmed x-y stage under a pressurized pen assembly mounted on a fixed z-axis. As the x-y table is moved, paste material is forced under pressure through a 1.times.10.sup.-2 cm (0.004 inch) carbide tip on the pen to write the identifying characters on the green sheet. Because the flow of paste material is hard to control, the identifying characters vary in size and shape and are difficult to read. Thus, a need exists for a method for the serizalation of ceramic substrates that produces uniform identifying characters that are easy to read and which is compatible with the process used for the manufacture of ceramic modules.